The sky wasn't really falling in autumn 2011; it just seemed that
way, with two defunct satellites plummeting to Earth out of
control within a month of each other.

First came NASA's
Upper Atmosphere Research Satellite, or UARS. This 6.5-ton
climate satellite, which was about the size of a school bus,
launched in 1991 and was decommissioned in 2005. UARS then spent
six years spiraling slowly toward our planet, finally plunging
into the atmosphere above the Pacific Ocean Sept. 24.

Germany's 2.7-ton Roentgen Satellite, or ROSAT, followed closely
on UARS' heels. This craft, which launched in 1990 to survey the
heavens in X-rays and was shut down in 1999, fell back to Earth
over the Indian Ocean Oct. 23.

Neither satellite crash injured anyone. But the sky isn't done
raining down huge pieces of space junk. Russia's failed Mars
probe Phobos-Grunt will soon plummet to Earth, perhaps even
before the year is out (see below). [ Vote
for the Best Spaceflight Story of 2011 ]

This year also saw the last flight of an American icon. NASA's
storied space shuttle program came to an end after 30 years of
service when Atlantis touched down shortly before dawn July 21.

Atlantis' flight was the 135th space mission for the shuttle
program, which began to take shape in 1972 and first launched to
orbit in 1981. The shuttle accomplished a great deal during its
long lifetime, helping to build the International Space Station
and making spaceflight more routine than it had been.

However, the shuttle's record highlights that spaceflight remains
a dangerous endeavor. Two of its 135 missions ended in tragedy,
killing a total of 14 astronauts. The shuttle Challenger exploded
shortly after liftoff in 1986, while Columbia broke up during
re-entry in 2003. [ NASA's
Space Shuttle Program in Pictures: A Tribute ]

The three remaining space-flown orbiters are now being prepped
for display in museums. For now, NASA is dependent on Russian
Soyuz vehicles to ferry its astronauts to and from low-Earth
orbit. However, the agency hopes private companies can take over
this orbital taxi service by 2017 or so.

3. A space first for China

Nov. 2 was a banner day for China and its space program. On that
date, the nation successfully docked two robotic spacecraft in
low-Earth orbit for the first time ever.

The mating of the two vehicles — called Shenzhou
8 and Tiangong 1 — was designed to test key technologies
that China will use to assemble a space station in orbit. The
country hopes to have a 66-ton manned station up and running by
2020.

And China won't rest on its laurels for long. The nation plans to
launch two more docking missions during 2012, at least one of
which will be manned.

4. 50 years of human spaceflight

The space shuttle program celebrated 30 years of spaceflight in
2011, but that anniversary took a back seat to a much bigger one
this year: 50 years of human spaceflight.

Yuri Gagarin became the
first person in space April 12, 1961, completing one Earth
orbit in his tiny Vostok capsule before returning safely to terra
firma less than two hours later. The United States launched its
first spaceflyer just weeks later, sending Alan Shepard on a
short suborbital flight May 5.

And the anniversaries didn't stop there. On May 25, 1961,
President John F. Kennedy made the speech that charted NASA's
direction for years to come, announcing that the United States
would put an astronaut on the moon before the end of the decade.

So while our future may be in the stars, this year spurred many
spaceflight experts and observers to cast their gaze back through
history.

5. The astronaut and the congresswoman

On Jan. 8, a gunman shot Arizona congresswoman Gabrielle Giffords
in the head as she talked to constituents outside a Tucson
grocery store. The attack left Giffords gravely wounded and six
other people dead.

The tragedy reverberated beyond Arizona and the halls of
Congress, reaching into low-Earth orbit. Giffords' husband, Mark
Kelly, was slated to command the STS-134 mission of the space
shuttle Endeavour — the second-to-last flight of the shuttle
program — just a few months after the shooting.

As Giffords made strides in her recovery, Kelly decided to take
part in the mission. When Endeavour blasted off from Florida's
Kennedy Space Center May 16, Giffords was in the crowd.

Kelly retired in October with four spaceflights under his belt.
Giffords continues to recuperate, and she's said she may
consider a return to Congress if her condition improves
enough.

6. NASA's uncertain future

In many ways, NASA had a great year in 2011. The agency launched
three different planetary missions, rendezvoused with the huge
asteroid Vesta and executed a comet flyby. And NASA's Kepler
space telescope discovered more than 2,000 potential alien
planets.

But the year also brought its share of transition and
uncertainty. With the space shuttle fleet retired, NASA is now
completely dependent on Russian Soyuz vehicles to ferry its
astronauts to and from the International Space Station, at $63
million per seat. NASA wants American private spaceflight
companies to take over this taxi service soon, but that probably
won't happen until 2017 at the earliest, officials have said.

NASA's budget
also keeps getting trimmed, as lawmakers look to cut federal
spending across the board. The agency may get just $17.4 billion
in fiscal year 2012, down from $18.5 billion in 2011.

The belt-tightening could threaten some of the agency's most
ambitious and expensive projects, including the $8.8-billion
James Webb Space Telescope (JWST). In July, the House
Appropriations Committee recommended canceling the huge
instrument, which is billed as the muscular successor to NASA's
Hubble Space Telescope.

Congress later restored funding for JWST, marking it as safe —
for now. The telescope is slated to launch in October 2018.

7. NASA's new rocket and spaceship

In 2010, President Barack Obama instructed NASA to work toward
getting astronauts to an asteroid by 2025 and to Mars by the
mid-2030s. This year, the space agency laid out how it plans to
reach these deep-space destinations.

The astronauts will ride aboard a new spaceship called the
Orion Multi-Purpose Crew Vehicle, which NASA announced in
May. The spacecraft is based heavily on the old Orion capsule
concept, which NASA began developing as part of its moon-oriented
Constellation program. The Obama Administration cancelled
Constellation last year in favor of the asteroid-first plan.

In September, NASA revealed its Space Launch System (SLS), the
$10-billion giant rocket that will lift Orion off the pad. In its
early incarnations, the SLS will likely be capable of lofting 70
tons of payload, but NASA eventually wants to beef it up to carry
130 tons of material to space.

2011 was a tough year for Russian spaceflight, as a string of
high-profile mishaps plagued the country.

On Feb. 1, for example, a Rockot launch vehicle failed to deliver
an Earth-observing satellite to the proper orbit. And on Aug. 18,
a Proton rocket didn't place a $300-million communications
satellite in the desired orbit.

Then, on Aug. 24, the unmanned Progress 44 supply ship crashed
while hauling cargo to the International Space Station, doomed by
a problem with the third stage of its Soyuz rocket. Russia uses a
similar version of the Soyuz to launch astronauts to the space
station, so manned flights were put on hold until the problem
with the rocket could be identified and fixed. As a result, the
orbiting lab operated with a skeleton crew of three astronauts
for a stretch this autumn.

Finally, the $165-million Mars moon probe Phobos-Grunt got stuck
in Earth orbit shortly after its Nov. 8 launch. The spacecraft's
thrusters were supposed to fire to send it on a course for the
Red Planet, but they never did so.

Phobos-Grunt is still circling our planet, its orbit getting
lower and lower by the day. Most experts consider the probe lost,
predicting that it will come crashing back into the atmosphere in
mid-January, though it's tough to peg an exact date. [ Photos:
Russia's Failed Phobos-Grunt Mission ]

In March, the space shuttle Discovery delivered NASA's final
contribution to the assembly of the orbiting lab, a new room
called the Permanent Multipurpose Module. While Russia may attach
one more module in the coming years, construction from a U.S.
standpoint is now 100-percent done.

NASA and its international partners began building the orbiting
lab in 1998. The 431-ton space station is as big as a football
field and has about as much living space as a five-bedroom house.
With an estimated price tag of $100 billion, the orbital outpost
is the most expensive structure ever built.

10. NASA launches its biggest Mars rover

NASA launched its own Mars mission Nov. 26, less than three weeks
after Russia's left the pad. But unlike Phobos-Grunt, the
$2.5-billion Mars Science Laboratory (MSL) mission is speeding
toward the Red Planet, apparently in perfect health.

MSL will drop the car-size Curiosity rover at Mars' huge Gale
Crater in August 2012, using a rocket-powered sky crane to lower
the robot to the planet's surface. Curiosity's main task is to
assess whether the Gale Crater area is, or ever was, capable of
supporting microbial life. [ Photos:
NASA's Curiosity Rover Launches to Mars ]

The 1-ton rover carries 10 instruments to help it answer this
question, including a rock-zapping laser and equipment designed
to identify organic compounds — carbon-based molecules that are
the building blocks of life as we know it.

11. Private spaceflight makes strides

A
private space race is developing among companies that hope to
ferry NASA astronauts to and from low-Earth orbit in the
post-shuttle era, and 2011 saw that race heat up.

Several different companies made strides this year in their
spacecraft development, ticking off key milestones that NASA laid
out for them as a condition of continued funding. The chief
contenders — firms such as Blue Origin, SpaceX, Boeing and Sierra
Nevada — generally say they should be ready to fly by 2015 or
2016.

Private suborbital spaceflight also made progress this year. The
space tourism company Virgin Galactic conducted more glide tests
of its SpaceShipTwo vehicle, and company officials have said that
in-vehicle rocket tests should start in the first half of 2012.

During commercial operations, SpaceShipTwo will take off from
Spaceport America, and this commercial facility really began
taking shape in 2011. Further, scientists put money down on the
research potential of suborbital spaceflight this year, buying
seats on SpaceShipTwo and XCOR Aerospace's Lynx vehicle.

You can follow SPACE.com senior writer Mike Wall on
Twitter:@michaeldwall.
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